Shear wall aspect ratio reducing frame (ARRF)

ABSTRACT

My invention, the Shear Wall Aspect Ratio Reducing Frame is a simple, economical, efficient, easy to install device that allows greater oppotunity and flexibility in the size and location of openings in the walls of wood frame constructed buildings particularly houses. The ARRF would replace the commercial, pre-fabricated systems now in use which are costly and inefficient labor-intensive shear wall devices. The ARRF achieves its goal by reducing the moment arm in the overturning equations that are used to determine the uplift forces in a shear wall. The ARRF reduces forces in walls rather than increase their bulk which is the strategic concept now in use throughout the design professions and the construction industry to solve the aspect ratio problem.

CROSS-REFERENCE TO RELATED APPLICATIONS

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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

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REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX

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BACKGROUND OF THE INVENTION

This invention pertains to the field of residential wood frame construction. There is a challenge in wood frame construction to resist loads on structures generated by lateral forces, i.e. wind and earthquakes. Most region of the United States are confronted by one or the other and in most areas—both.

Lateral forces are typically resisted by shear walls in economical wood frame construction or, when the aspect ratio of two to one is exceeded Two being the heighth and one being the width, by pre-fabricated heavy duty “strong walls”. Due to the expense and complexity of strong wall assemblies, residential house designers try to avoid using walls that have an excessive aspect ratio. The two to one limit is code mandated for non-strong-wall construction.

A specific existing problem with the three most prominent commercially available pre-fabricated strong walls: Simpson Strong Wall, Hardy Frame and Truss-Joist Shear Panel is that they are costly and they require a highly skilled carpenter and considerable site preparation for their installation. They all require significant precision in the installation of their anchorage components and care in their attachment to adjacent components of the wood frame. They require close tolerances for tight fit. They are tall and heavy and the smallest of them require two men to lift and to install.

The Shear Wall Aspect Ratio Reducing Frame henceforth referred to as the ARRF is very forgiving in its installation into the foundation formwork prior to the pouring of concrete and the ARRF can be installed by a single moderately skilled worker who is not necessarily an experienced carpenter.

BRIEF SUMMARY OF THE INVENTION

This invention, the ARRF, reduces forces on a shear wall by 50% making it unnecessary to provide a full heighth, heavy duty, pre-fabricated strong wall shear walls in narrow shear resisting sections of wall. The aforementioned manufacturers of high-strength walls provide greater shear force resisting capacity than that provided by conventional wood frame construction by means of heftier components without regard to the aspect ratio of the wall. These products increase shear capacity (pounds per foot of resistance) and uplift force resistance capacity (pounds of force) by bulk increases in the size and strength of their respective assemblies as well as from stronger connections of those pieces to each other and to the adjacent reinforced concrete foundation (lower connection) and the top plate (upper connection).

This invention, the ARRF, reduces the aspect ratio of a narrow wall to a size that is greater than the code mandated minimum (2:1) thus allowing standard construction between the ARRF and the top plate. The ARRF reduces the uplift forces that are generated by lateral force induced overturning moments in the wood frame wall components by half i.e a 10,000 pound uplift force is reduced to a 5,000 pound uplift force.

The ARRF is only one-half as high as the wall in which it is placed which makes it easy to install. The ARRF does not have to fit into a precise zone as defined by the top surface of the concrete stem wall and the underside of the top plate as is the case for all other pre-fabricated strong walls. The ARRF is easy to install using semi-skilled workers.

In summary, instead of increasing force resisting capacity by being heavier, and more complex, the ARRF reduces these forces themselves with a simple device that is, in effect, an extension of the top plane of the stem wall of the foundation. As a result of reducing the vertical distance (moment arm) between the lateral force induced by the diaphragm action of the roof or second floor and the solid connection to the foundation, the forces in the wall are reduced to a level that is managable by standard construction

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a top view of the ARRF. This device consists of two parts welded together, a tube steel frame that acts as a vierendeel truss and a rebar base. The tube steel upper section is made of 3″×3″×¼″ ASTM A-36 straight steel stock whose pieces are welded together with ER70S-3 rod, ¼″ welds all around at each of six joints. The welded square tube assembly is cleaned, primed and painted. Prior to priming/painting, this tube steel assembly is welded at its bottom most surface to a single Number 8 (1″ diameter) shaped rebar made of ASTM A-36 60 ksi steel.

After the upper and lower parts are welded together, the tube steel section is primed and painted. The rebar is cleaned and left uncoated to ensure maximum bond to the concrete in which it is located.

FIG. 2 is a front elevation of the ARRF as it would appear looking toward the exterior wall of a house from the yard.

FIG. 3 is a side elevation of the ARRF showing its tube steel upper section and its rebar lower section. The rebar is angled in toward the center of the stem wall to ensure proper concrete cover. Two pairs of threaded rods are located on the ARRF. The top pair and the bottom pair are both made of ⅝″ threaded stock and welded to the frame. The top pair secure the elevated sole plate for the anchorage of the low end of the intermediate stud, the lower pair secure the mudsill as would an anchor bolt.

FIGS. 4,5,6 show the ARRF in the context of a wood framed wall. The wall shown would have an excessive aspect ratio were it not for the ARRF.

DETAILED DESCRIPTION OF THE INVENTION

The ARRF is a shop-fabricated steel device that is installed in the foundation of a house prior to the pouring of the concrete for the foundation. During shop fabrication the five straight tube steel pieces are set in a jig and welded together. The threaded steel rods are welded into place. The rebar lower section is bent into its specified configuration, internally welded where required and then welded to the bottom of the now assembled (welded) tube steel section. The entire assembly is cleaned with acetone or equal, the rebar lower section is masked and the tube steel upper section is primed and painted. The ARRF is now ready to be transported to the construction site

DETAILED DESCRIPTION OF THE INVENTION (continued)

After the house foundation formwork has been installed, the rebar section of the ARRF is placed on dobies (small concrete spacers) and wire-tied to the adjacent formwork ensuring that it is straight, level and plumb. The foundation rebar is installed and tied to the ARRF rebar component. Concrete is poured thus securing the ARRF in its permanent position.

The traditional wood frame components are erected around the ARRF and it takes its place in the assembled frame components to fulfill its lateral force resisting task.

LEGEND

-   1 ⅝″ diameter×3″ steel threaded rod -   2 3″×3″×¼″ tube steel frame -   3 3″×3″×¼″ tube steel horizontal brace -   4 ⅝″ diameter×4″ steel threaded rod -   5 ¼″ continuous welds -   6 Number 8 (1″ diameter) re-bar -   7 Mudsill -   8 Reinforced concrete stemwall -   9 Reinforced concrete footing -   10 Wood post -   11 Anchor bolt -   12 Top plate -   13 Header @ adjacent opening -   14 Stud -   15 Holddown bracket -   16 Sole plate -   17 Subfloor -   18 Rim joist -   19 Mudsill -   20 Floor joist 

1. I claim my invention, the Shear Wall Aspect Ratio Reducing Frame (ARRF) is a component in wood frame construction that reduces the aspect ratio of shear walls to a level acceptable to building officials (building codes) thus making pre-fabricated, full height, heavy duty shear walls unnecessary. 